--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/testsuite/gcc.dg/parm-impl-decl-1.c	Fri Oct 27 22:46:09 2017 +0900
@@ -0,0 +1,33 @@
+/* Test implicit function declarations and other odd declarations in
+   function prototypes.  Bug 18239.  */
+/* Origin: Joseph Myers <joseph@codesourcery.com> */
+/* { dg-do compile } */
+/* { dg-options "-std=gnu89" } */
+
+/* Implicit function declaration in attribute in definition (testcase
+   from bug).  */
+int
+foo (int __attribute__ ((__mode__ (vector_size(8)))) i) /* { dg-warning "'mode' attribute ignored" } */
+{
+  return (long long) i;
+}
+
+/* Various other cases.  */
+
+int f (int [sizeof(g())]);
+int f1 (int [sizeof(g1())]);
+
+int g () { return 1; }
+
+int
+h (int (*p)[sizeof(i())])
+{
+  int g2 (), g3 ();
+  return (*p)[0] + g3() + g2();
+}
+
+int i () { return 2; }
+
+int f2 (int [sizeof(g2())]);
+int f3 (int [sizeof(g3())]);
+int g3 () { return 4; }